1. Field of the Invention
The present invention relates to a semiconductor device with a Schottky contact, and a method for forming a Schottky contact in a semiconductor device.
2. Background of the Related Art
Recently, GaN group compound semiconductors are widely used in semiconductor devices, such as field effect transistors and diodes. For an example, in fabrication of related art GaN group field effect transistors, for rectifying junction of a gate electrode, either single metal, such as Pt, Pd, Au, Ni, or multi-layer of metals, such as Au/Ni, Au/Pt are used. In order to form a rectifying metal junction on an undoped GaN thin film and an xe2x80x98nxe2x80x99 type GaN thin film, the single metal or the multi-layer of metals are used widely. Of the metals, Pt forms the most excellent rectifying junction on the GaN thin film. Pt also has a high melting point, an excellent chemical resistance, as well as a high work function of approx. 5.65 eV. Moreover, Pt forms a junction potential barrier of a height approx. 1.20xcx9c1.27 eV at junction with the GaN thin film. Besides the GaN, ternary compounds, such as AlGaN and InGaN, are stable to heat and chemical, and have an excellent physical strength. The ternary compounds are materials the most suitable for blue and green light emitting devices and UV ray detecting devices as the ternary compounds have an energy gap in a range of 1.9xcx9c6.2 eV. As explained, those GaN group compound semiconductors, of which study is started for development of the blue light emitting devices, has, not only a high saturated electron velocity, a high breakdown voltage, and a high thermal conductivity, but also a high two dimensional electron concentration, and a high electron mobility owing to a great difference of conduction band energies when a hetero-junction of AlGaN/GaN is formed. Accordingly, there have been many researches on the GaN group compound semiconductors for application to electronic devices, recently. Of the electronic devices and the optical devices of the GaN group compound semiconductors, devices of MESFET, HFET and UV detectors are under research the most actively. As results of the researches, performances of the devices are excellent close to levels to put into practical use. In fabrication of the field effect transistors, since a gate rectifying junction gives a great influence to device characteristics, there are many reports on researches for improving the characteristics.
However, the foregoing related art method for forming a Schottky contact has the following problems.
In fabrication of electronic devices of field effect transistors having excellent operational characteristics at an elevated temperature, the rectifying junctions are formed by using the GaN group compound semiconductors and metals, such as Pt, used presently. The GaN group compound semiconductors and the metals inclusive of Pt show significantly poor characteristics at an elevated temperature. Therefore, it is difficult to fabricate high powered devices for operation at an elevated temperature, of metals currently used the mostly, inclusive of the GaN group compound semiconductors and Pt.
Accordingly, the present invention is directed to a semiconductor device with a Schottky contact, and a method for forming a Schottky contact in a semiconductor device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method for forming a Schottky contact in a semiconductor device, which permits fabrication of a high powered semiconductor device operable at an elevated temperature.
Another object of the present invention is to provide a method for forming a Schottky contact in a semiconductor device, which permits to obtain a rectifying junction having an excellent thermal characteristic, chemical characteristic, and an electrical characteristic.
Further object of the present invention is to provide a semiconductor device having an excellent Schottky contact.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
The present invention is characterized in that ruthenium and ruthenium oxides are employed as a rectifying junction metal of a GaN group compound semiconductor. The ruthenium and ruthenium oxides are favorable for fabrication of high powered devices operable at an elevated temperature owing to excellent electrical characteristics and stable to heat and chemical.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, at first an n type GaN group compound semiconductor layer is prepared. Then, at least one metal layer including a ruthenium component layer as a rectifying junction metal is formed on the n type GaN group compound semiconductor layer.
Preferably, the rectifying junction metal including the ruthenium component layer may be any one selected from RuO2, Ru, RuO2/Ru, Ru/RuO2, Au/RuO2, Au/Ru, Au/RuO2/Ru, and Au/Ru/RuO2.
Preferably, an upper layer of the rectifying junction metal including the ruthenium component layer is formed of any one material selected from RuO2, Ru, RuO2/Ru, and Ru/RuO2, and a lower layer thereof is formed of at least one layer of a material selected from Pt, Pd, Ni, Au, Al, W, WSi, Zn, Ta, Ti, Co, and In.
Preferably, the at least one layer of rectifying junction metal including ruthenium or ruthenium oxide may be heat treated at an elevated temperature ranging 300xc2x0 C.-600xc2x0 C. under an ambient of at least one gas selected from oxygen, nitrogen, argon, and air, or of a mixed gas, or of a vacuum, or may not be heat treated.
In fabrication of electronic devices and optical devices, ruthenium or a ruthenium oxide is employed as a rectifying junction meta. The ruthenium and ruthenium oxides have a low cost, are stable to heat and chemicals, and have excellent electric characteristics, thereby improving a high temperature performance and an UV ray detection performance of the semiconductor devices, such as the electronic devices and the optical devices.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.